JP3370123B2 - Combustion chamber structure of direct injection diesel engine - Google Patents
Combustion chamber structure of direct injection diesel engineInfo
- Publication number
- JP3370123B2 JP3370123B2 JP01245693A JP1245693A JP3370123B2 JP 3370123 B2 JP3370123 B2 JP 3370123B2 JP 01245693 A JP01245693 A JP 01245693A JP 1245693 A JP1245693 A JP 1245693A JP 3370123 B2 JP3370123 B2 JP 3370123B2
- Authority
- JP
- Japan
- Prior art keywords
- combustion chamber
- annular space
- fuel flow
- opening
- protrusion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
- F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
- F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
- F02B23/0645—Details related to the fuel injector or the fuel spray
- F02B23/0648—Means or methods to improve the spray dispersion, evaporation or ignition
- F02B23/0651—Means or methods to improve the spray dispersion, evaporation or ignition the fuel spray impinging on reflecting surfaces or being specially guided throughout the combustion space
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
- F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
- F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
- F02B23/0672—Omega-piston bowl, i.e. the combustion space having a central projection pointing towards the cylinder head and the surrounding wall being inclined towards the cylinder center axis
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B2275/00—Other engines, components or details, not provided for in other groups of this subclass
- F02B2275/14—Direct injection into combustion chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B23/00—Other engines characterised by special shape or construction of combustion chambers to improve operation
- F02B23/02—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition
- F02B23/06—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston
- F02B23/0618—Other engines characterised by special shape or construction of combustion chambers to improve operation with compression ignition the combustion space being arranged in working piston having in-cylinder means to influence the charge motion
- F02B23/0624—Swirl flow
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B3/00—Engines characterised by air compression and subsequent fuel addition
- F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Dispersion Chemistry (AREA)
- Combustion Methods Of Internal-Combustion Engines (AREA)
Description
【０００１】[0001]
【産業上の利用分野】この発明は、燃焼室を形成する凹
陥部がピストンの頂面に設けられた直噴式ディーゼルエ
ンジンの燃焼室構造の改良に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a combustion chamber structure of a direct injection diesel engine in which a recessed portion forming a combustion chamber is provided on the top surface of a piston.
【０００２】[0002]
【従来の技術】従来より、この種直噴式ディーゼルエン
ジンのピストンの頂面に形成される凹陥部内の燃焼室と
しては、リエントラント型やトロイダル型の燃焼室が主
流とされているが、吸気（空気）が吸気ポートからシリ
ンダ内に流入する際に生成されるスワールを燃焼行程の
終期まで持続させることは難しく、その吸気スワールに
より燃焼性を高めて排気ガス中のパティキュレート（可
燃性微粒子）を低減するという面からみれば不十分であ
る。2. Description of the Related Art Conventionally, a reentrant type or toroidal type combustion chamber has been mainly used as a combustion chamber in a concave portion formed on the top surface of a piston of a direct injection diesel engine of this type. ) Is difficult to maintain until the end of the combustion stroke, which is generated when the air flows from the intake port into the cylinder. The intake swirl enhances combustibility and reduces particulates (combustible particles) in the exhaust gas. It is insufficient from the viewpoint of doing.
【０００３】このような吸気スワールの持続性を高める
ようにした燃焼室構造として、従来、特開昭６３―１６
２９２５号公報に開示されるものが知られている。この
ものでは、図３に示すように、ピストン２１頂面の、燃
焼室２４を形成するための凹陥部２３は基本的に奥部側
の内径が開口部２２よりも大きい形状とされ、この凹陥
部２３の底面中央に開口部２２側に突出する突起部２６
が形成されていて、この突起部２６の先端外周部に凹陥
部２３の奥部側に向かって外径が拡大する突起部テーパ
面２７が開口部２２と対峙するように設けられている。
さらに、上記突起部テーパ面２７の外周部と開口部２２
との間には断面略円形状の環状空間２５が突起部２６を
取り囲むように設けられている。Ｏs は環状空間２５の
断面中心である。そして、ピストン２１が上死点近傍に
ある圧縮行程の終期でシリンダヘッド側の燃料噴射ノズ
ル（いずれも図示せず）から燃料が噴射されたとき、そ
の一部の燃料流Ｆが、突起部２６先端のテーパ面２７と
それに対峙する凹陥部２３の開口部２２との間を通って
環状空間２５の壁面（凹陥部２３の側壁）に衝突して、
吸気スワールとのミキシングが図られるようになってい
る。As a combustion chamber structure for enhancing the sustainability of such an intake swirl, there is a conventional Japanese Patent Laid-Open No. 63-16.
The one disclosed in Japanese Patent No. 2925 is known. In this case, as shown in FIG. 3 , the recessed portion 23 on the top surface of the piston 21 for forming the combustion chamber 24 is basically shaped such that the inner diameter on the inner side is larger than that of the opening 22. A protrusion 26 protruding toward the opening 22 at the center of the bottom surface of the portion 23.
Is formed, and a projection tapered surface 27 whose outer diameter increases toward the inner side of the recess 23 is provided on the outer periphery of the tip of the projection 26 so as to face the opening 22.
Further, the outer peripheral portion of the projection tapered surface 27 and the opening 22 are
An annular space 25 having a substantially circular cross section is provided between and so as to surround the protrusion 26. Os is the center of the cross section of the annular space 25. Then, when fuel is injected from the fuel injection nozzle (neither is shown) on the cylinder head side at the end of the compression stroke in which the piston 21 is near the top dead center, a part of the fuel flow F is generated by the protrusion 26. It collides with the wall surface of the annular space 25 (the side wall of the concave portion 23) through a space between the tapered surface 27 at the tip and the opening 22 of the concave portion 23 facing it,
Mixing with the intake swirl is designed.
【０００４】[0004]
【発明が解決しようとする課題】この提案のものでは、
上記突起部２６先端のテーパ面２７とそれに対峙する開
口部２２との間の距離が環状空間２５の内径よりも短い
ので、その部分で吸気が絞られるようになり、シリンダ
内から凹陥部２３内の燃焼室２４に向かう吸気スワール
の強度が大きくなってその持続性を向上させることがで
きる。[Problems to be Solved by the Invention]
Since the distance between the tapered surface 27 at the tip of the protruding portion 26 and the opening 22 facing it is shorter than the inner diameter of the annular space 25, the intake air can be throttled at that portion, and the inside of the cylinder from the recessed portion 23 can be throttled. The strength of the intake swirl heading toward the combustion chamber 24 is increased and the sustainability thereof can be improved.
【０００５】ところが、環状空間２５の壁面は断面略円
形状であるので、燃料噴射ノズルから噴射された燃料流
Ｆは環状空間２５の壁面に衝突した後、その壁面に沿っ
て比較的スムーズに凹陥部２３の奥部側に向かうように
なり、噴射燃料を吸気と十分にミキシングすることがで
きず、パティキュレートの低減に限度がある。However, since the wall surface of the annular space 25 has a substantially circular cross section, the fuel flow F injected from the fuel injection nozzle collides with the wall surface of the annular space 25, and then is recessed relatively smoothly along the wall surface. As it goes toward the inner side of the portion 23, the injected fuel cannot be sufficiently mixed with the intake air, and there is a limit to the reduction of particulates.
【０００６】本発明は斯かる諸点に鑑みてなされたもの
で、その目的は、上記した燃焼室の形状、構造を改良す
ることで、吸気スワールの持続性をさらに向上させなが
ら、噴射燃料が燃焼室壁面に衝突した後の流れを乱して
吸気とのミキシング性を高め、よってパティキュレート
のより一層の低減を図ることにある。The present invention has been made in view of the above points, and an object thereof is to improve the shape and structure of the above-mentioned combustion chamber to further improve the sustainability of the intake swirl while the injected fuel burns. The purpose of this is to disturb the flow after colliding with the wall surface of the chamber to enhance the mixing property with the intake air, thereby further reducing the particulates.
【０００７】[0007]
【課題を解決するための手段】上記の目的を達成すべ
く、請求項１の発明では、凹陥部内の燃焼室の一部を構
成する環状空間の壁面のうち、燃料の噴射流が衝突した
後に向かう部分の断面形状を他の部分よりも小径の円弧
状とした。In order to achieve the above-mentioned object, in the invention of claim 1, after the fuel injection flow collides with the wall surface of the annular space forming a part of the combustion chamber in the recessed portion, The cross-sectional shape of the facing portion was an arc shape having a smaller diameter than the other portions.
【０００８】すなわち、この発明では、上記の如く、ピ
ストンの頂面に、奥部側の内径が開口部よりも大きくて
燃焼室を形成する凹陥部が設けられ、上記凹陥部の底面
中央に凹陥部の開口側に突出する突起部が形成されてい
て、この突起部の先端外周部に凹陥部の奥部側に向かっ
て外径が拡大する突起部テーパ面が凹陥部の開口部と対
峙するように形成され、上記突起部の外周部と凹陥部の
開口部との間に断面略円形状の環状空間が突起部を取り
囲むように設けられた直噴式ディーゼルエンジンの燃焼
室構造が前提である。That is, according to the present invention, as described above, the top surface of the piston is provided with the recessed portion having the inner diameter on the inner side larger than that of the opening to form the combustion chamber, and the recessed portion is formed at the center of the bottom surface of the recessed portion. A protrusion protruding toward the opening of the recess, and a tapered surface of the protrusion whose outer diameter increases toward the inner side of the recess at the outer periphery of the tip of the protrusion faces the opening of the recess. It is premised on the combustion chamber structure of the direct injection diesel engine in which an annular space having a substantially circular cross section is provided between the outer periphery of the protrusion and the opening of the recess so as to surround the protrusion. .
【０００９】そして、上記環状空間の壁面のうち、凹陥
部の外周縁部でかつ上記開口部近傍の位置には、該環状
空間の断面中心を中心とする所定半径の円弧面からなっ
ていて燃料噴射ノズルから噴射される燃料流が衝突する
燃料流衝突部を設ける一方、上記環状空間の壁面のうち
上記燃料流衝突部の奥端部側の位置には、燃料流衝突部
の円弧面の半径よりも小径でかつ該燃料流衝突部の円弧
面よりも半径方向外側に位置する小径円弧部を他の壁面
と連続するように設ける。さらに、上記突起部 テーパ面
を断面略円弧状に凹陥させる。 On the wall surface of the annular space, at the position of the outer peripheral edge of the recess and in the vicinity of the opening , there is formed an arc surface having a predetermined radius centered on the center of the cross section of the annular space.
And the fuel flow injected from the fuel injection nozzle collides
While providing the fuel flow collision part, among the wall surfaces of the annular space
At the position on the far end side of the fuel flow collision part, the fuel flow collision part
Is smaller than the radius of the arc surface of and the arc of the fuel flow collision part
A small-diameter circular arc located radially outside the surface
And it provided so as to continuous. Furthermore, the above-mentioned tapered portion
Is recessed in an arc shape in cross section.
【００１０】尚、上記小径円弧部の断面半径ｒは、凹陥
部の開口半径をＲc とするとき、０．０４Ｒc ＜ｒ＜
０．３６Ｒc の範囲であり、望ましくは０．０８Ｒc ＜
ｒ＜０．２４Ｒc がよい。すなわち、ｒ≧０．３６Ｒc
であれば、スワールの持続性及び乱れが小となり、空気
と燃料とのミキシングが良好とならない一方、ｒ≦０．
０４Ｒc では、燃焼室の加工上の問題が生じると予測さ
れる。The cross-sectional radius r of the small-diameter circular arc portion is 0.04Rc <r <when the opening radius of the recess is Rc.
The range is 0.36 Rc, preferably 0.08 Rc <
r <0.24Rc is preferable. That is, r ≧ 0.36Rc
If so, the sustainability and turbulence of the swirl will be small, and the mixing of air and fuel will not be good, while r ≦ 0.
At 04Rc, problems in the processing of the combustion chamber are predicted to occur.
【００１１】請求項２の発明では、さらに、上記環状空
間の壁面における小径円弧部の半径方向内側に、凹陥部
の奥部側に向かって外径が拡大するテーパ面部を小径円
弧部に連続するように形成する。[0011] In the present invention of claim 2, further connection with the radially inner side of the small-diameter arcuate portion of the wall surface of the annular space, the tapered surface portion of enlarged outer diameter toward the innermost side of the recessed portion to the small-diameter arcuate portion To be formed.
【００１２】[0012]
【作用】上記の構成により、請求項１の発明では、環状
空間の壁面のうち凹陥部の外周縁部でかつ奥端部側に相
当する壁面に小径円弧部が形成され、この小径円弧部は
環状空間の壁面の燃料流衝突部の円弧面よりも半径方向
外側に位置して、その円弧半径は上記燃料流衝突部の円
弧面の半径よりも小径であるので、この小径円弧部が燃
料流衝突部の位置から半径方向外側に突出している分だ
け、該小径円弧部近傍で環状空間内の慣性モーメントが
大となり、燃焼室での吸気スワールの持続性がさらに高
まって、燃焼行程の終期まで持続することとなる。そし
て、このピストンの上死点近傍で燃料噴射ノズルから燃
料が燃焼室に向けて噴射され、その燃料流が突起部先端
のテーパ面とそれに対峙する凹陥部の開口部との間を通
って環状空間の壁面のうちの上記燃料流衝突部に衝突す
ると、この衝突後の燃料は凹陥部の奥部に向かうが、そ
の前方には上記小径円弧部が形成されているため、そこ
でのエッジ効果を受けて乱れることとなる。しかも、こ
の小径円弧部では上記の如く強い吸気スワールが生成さ
れているので、これらの相乗効果により燃料の吸気との
ミキシング性が大幅に増大し、その燃焼性を高めてパテ
ィキュレートを効果的に低減することができる。With the above construction, in the invention of claim 1, a small-diameter circular arc portion is formed on the wall surface of the annular space which is the outer peripheral edge portion of the concave portion and corresponds to the rear end side. It is located radially outside the arc surface of the fuel flow collision portion on the wall surface of the annular space, and the arc radius is the circle of the fuel flow collision portion.
Since a smaller diameter than the radius of the arc surface, the small-diameter arcuate portion retardant
The moment of inertia in the annular space in the vicinity of the small-diameter circular arc portion becomes large as much as it protrudes outward in the radial direction from the position of the charge flow collision portion , further increasing the sustainability of the intake swirl in the combustion chamber, and It will continue until the end. Then, in the vicinity of the top dead center of the piston, fuel is injected from the fuel injection nozzle toward the combustion chamber, and the fuel flow passes between the tapered surface at the tip of the protrusion and the opening of the concave portion facing the annular surface. When colliding with the fuel flow collision part of the wall surface of the space, the fuel after this collision goes to the inner part of the concave part, but since the small diameter circular arc part is formed in front of it, the edge effect there is It will be received and disturbed. Moreover, since the strong intake swirl is generated in the small-diameter circular arc portion as described above, the synergistic effect of these greatly increases the mixing property of the fuel with the intake air, and enhances the combustion property of the particulates effectively. It can be reduced.
【００１３】また、ピストンの上昇行程で燃焼室内の環
状空間に導入される吸気は、突起部先端のテーパ面とそ
れに対峙する凹陥部の開口部との間で絞られるが、上記
突起部テーパ面が断面略円弧状に凹陥されているので、
この凹陥構造により、上記環状空間に向かう吸気の一部
が突起部テーパ面から離れて開口部側、つまり燃料噴射
ノズルからの燃料流に向かうように案内される。そし
て、燃料噴射ノズルから燃料が噴射されたとき、その燃
料流は周辺の吸気を巻き込みながら飛ぶが、この燃料流
に向かう上記吸気により燃料への吸気の巻込み度が増大
し、燃料への吸気導入率が高まってミキシング効果がさ
らに向上し、パティキュレートの低減により一層有効と
なる。 Also, during the ascending stroke of the piston, the ring in the combustion chamber is
The intake air introduced into the space is shaped like a tapered surface at the tip of the protrusion.
It is squeezed between the opening of the recess facing it,
Since the projection tapered surface is recessed in a substantially arcuate cross section,
Due to this concave structure, part of the intake air that goes to the annular space
Is on the opening side away from the tapered surface of the protrusion, that is, fuel injection
Guided towards the fuel flow from the nozzle. That
When fuel is injected from the fuel injection nozzle,
The fuel flow flies while entraining the intake air around it, but this fuel flow
The degree of entrainment of the intake air into the fuel is increased by the above intake air toward the
However, the rate of introduction of intake air into the fuel is increased and the mixing effect is improved.
Further improved and more effective by reducing particulates
Become.
【００１４】請求項２の発明では、環状空間の壁面にお
ける小径円弧部の半径方向内側に、凹陥部の奥部側に向
かって外径が拡大するテーパ面部が形成されているの
で、このテーパ面部により、燃焼室の一部が断面略円形
状の環状空間とされた従来のディーゼルエンジンと比較
して燃焼室の容積、換言すれば圧縮比を変えることな
く、上記効果が得られる。 [0014] The In the present invention of claim 2, radially inwardly of the small diameter arc portion on the wall surface of the annular space, tapered surface portion having an outer diameter expands toward the innermost side of the recessed Recessed portions are formed
With this tapered surface portion , the above effect can be obtained without changing the volume of the combustion chamber, in other words, the compression ratio, as compared with the conventional diesel engine in which a part of the combustion chamber is an annular space having a substantially circular cross section. It is.
【００１５】[0015]
【実施例】以下、本発明の実施例を図面に基づいて説明
する。Embodiments of the present invention will be described below with reference to the drawings.
【００１６】（参考例）
図１は参考例に係る直噴式ディーゼルエンジンの燃焼室
構造を示す。この図１において、１は直噴式ディーゼル
エンジンのピストンで、シリンダ（図示せず）内で往復
動するものである。ピストン１の頂面には基本的に奥部
側の内径が開口部２よりも大きい形状とされた凹陥部３
が形成され、上記開口部２はピストン１の中心線と平行
で半径Ｒc の円筒面とされている。上記凹陥部３内は燃
焼室４とされ、この凹陥部３の底面中央には開口部２側
に突出する突起部６が形成され、この突起部６の先端外
周部には凹陥部３の奥部側に向かって外径が拡大する突
起部テーパ面７が開口部２と対峙するように設けられて
いる。 Reference Example FIG. 1 shows a combustion chamber structure of a direct injection diesel engine according to a reference example . In FIG. 1, reference numeral 1 denotes a piston of a direct injection diesel engine, which reciprocates in a cylinder (not shown). The top surface of the piston 1 is basically a recessed portion 3 whose inner diameter on the inner side is larger than that of the opening 2.
And the opening 2 is a cylindrical surface parallel to the center line of the piston 1 and having a radius Rc. The interior of the recess 3 is a combustion chamber 4, and a protrusion 6 protruding toward the opening 2 is formed in the center of the bottom surface of the recess 3. The outer periphery of the tip of the protrusion 6 is deep inside the recess 3. A projection tapered surface 7 having an outer diameter increasing toward the side is provided so as to face the opening 2.
【００１７】上記突起部テーパ面７の外周部と凹陥部３
の開口部２との間には、突起部テーパ面７の外周部から
凹陥部３の開口部２に亘る壁面を有する断面略円形状の
環状空間５が突起部６を取り囲むようにそれと同心に設
けられている。この環状空間５の壁面のうち凹陥部３の
開口部２近傍が燃料流衝突部８とされ、この燃料流衝突
部８は、環状空間５の断面中心Ｏs を中心としかつ壁面
上を通る所定半径Ｒの基準円弧面Ｐ上に位置している。
そして、シリンダの圧縮行程でピストン１が上死点近傍
に上昇したとき、シリンダヘッド側の燃料噴射ノズル
（いずれも図示せず）から噴射された一部の燃料流Ｆが
上記突起部６先端のテーパ面７とそれに対峙する開口部
２との間を通って環状空間５内に向かい、その壁面（凹
陥部３の側壁）の一部たる上記燃料流衝突部８に衝突す
るようになっている。The outer peripheral portion of the taper surface 7 of the protrusion and the concave portion 3
Between the opening 2 and the opening 2, the annular space 5 having a substantially circular cross section having a wall surface extending from the outer peripheral portion of the projection tapered surface 7 to the opening 2 of the recess 3 is concentrically formed so as to surround the projection 6. It is provided. A portion of the wall surface of the annular space 5 near the opening 2 of the recess 3 is a fuel flow collision portion 8, and the fuel flow collision portion 8 has a predetermined radius centered on the cross-sectional center Os of the annular space 5 and passing on the wall surface. It is located on the reference arc surface P of R.
Then, when the piston 1 rises near the top dead center in the compression stroke of the cylinder, a part of the fuel flow F injected from the fuel injection nozzle on the cylinder head side (neither is shown) is transferred to the tip of the protrusion 6. It goes through the space between the tapered surface 7 and the opening 2 facing it into the annular space 5, and collides with the fuel flow collision portion 8 which is a part of the wall surface (side wall of the recessed portion 3). .
【００１８】さらに、上記環状空間５の壁面のうち、燃
料流衝突部８よりも凹陥部３の奥端部側に相当する壁面
には、上記環状空間５の断面中心Ｏs を中心とする半径
Ｒの基準円弧面Ｐの位置よりも凹陥部３の半径方向外側
に位置しかつ基準円弧面Ｐの半径Ｒよりも小径の半径ｒ
を有する小径円弧部９が設けられ、この小径円弧部９の
開口部２側縁部は上記燃料流衝突部８の下縁部と滑らか
に連続し、両者の境界部分はピストン１の中心線と平行
な円筒面（垂直面）とされている。Further, among the wall surfaces of the annular space 5, the wall surface corresponding to the rear end side of the recessed portion 3 with respect to the fuel flow collision portion 8 has a radius R about the cross-sectional center Os of the annular space 5. Radius r of the radius of the reference arc surface P that is located outside of the reference arc surface P in the radial direction of the concave portion 3 and smaller than the radius R of the reference arc surface P.
Is provided, and the edge portion of the small diameter arc portion 9 on the side of the opening 2 is smoothly continuous with the lower edge portion of the fuel flow collision portion 8, and the boundary portion between them is the center line of the piston 1. It is a parallel cylindrical surface (vertical surface).
【００１９】尚、上記小径円弧部９の断面半径ｒは、上
記凹陥部３の開口部２の半径Ｒc に対し、ｒ≧０．３６
Ｒc であれば、スワールの持続性及び乱れが小となり、
空気と燃料とのミキシングが良好とならない一方、ｒ≦
０．０４Ｒc では、燃焼室の加工上の問題が生じると予
測されるので、０．０４Ｒc ＜ｒ＜０．３６Ｒc の範囲
とするのがよく、より望ましくは０．０８Ｒc ＜ｒ＜
０．２４Ｒc がよい。The sectional radius r of the small-diameter circular arc portion 9 is r ≧ 0.36 with respect to the radius Rc of the opening 2 of the recessed portion 3.
With Rc, swirl persistence and turbulence are small,
While mixing of air and fuel is not good, r ≦
Since 0.04Rc is expected to cause a problem in the processing of the combustion chamber, it is preferable to set it in the range of 0.04Rc <r <0.36Rc, more preferably 0.08Rc <r <
0.24 Rc is good.
【００２０】また、上記環状空間５の壁面における小径
円弧部９と突起部テーパ面７の外周部との間には、上記
環状空間５の断面中心Ｏs を中心としかつ壁面上を通る
基準円弧面Ｐの位置よりも半径方向内側に位置し凹陥部
３の奥部側に向かって外径が拡大するテーパ面部１０が
形成され、このテーパ面部１０の外周縁部は上記小径円
弧部９の内周縁部に、またその内周縁部は突起部テーパ
面７外周側の環状空間５壁面にそれぞれ滑らかに連続し
ている。Further, between the small-diameter circular arc portion 9 on the wall surface of the annular space 5 and the outer peripheral portion of the projection tapered surface 7, there is a reference circular arc surface centered on the sectional center Os of the annular space 5 and passing on the wall surface. A tapered surface portion 10 that is located radially inward of the position P and has an outer diameter that increases toward the inner side of the recessed portion 3 is formed. The outer peripheral edge portion of the tapered surface portion 10 is the inner peripheral edge of the small-diameter circular arc portion 9. And the inner peripheral edge thereof are smoothly continuous to the wall surface of the annular space 5 on the outer peripheral side of the projection tapered surface 7.
【００２１】したがって、上記参考例においては、シリ
ンダ内でピストン１が下降移動する吸気行程でシリンダ
内に吸入される吸気（空気）にスワールが生成され、そ
の後、シリンダの圧縮行程でピストン１が上昇すると、
上記スワールはピストン１頂面の凹陥部３内の燃焼室４
に押し込められ、その流速が上昇する。そして、上記環
状空間５の壁面のうち、凹陥部３の外周縁部でかつ奥端
部側に相当する壁面に小径円弧部９が形成され、この小
径円弧部９は環状空間５の断面中心Ｏs を中心としかつ
壁面上を通る半径Ｒの基準円弧面Ｐの位置よりも半径方
向外側に位置し、その円弧半径ｒは上記基準円弧面Ｐの
半径Ｒよりも小径であるので、この小径円弧部９が基準
円弧面Ｐの位置から外側に突出している分だけ、慣性モ
ーメントが大となり、燃焼室４での吸気スワールの持続
性がさらに高まって燃焼行程の終期まで強く持続する。Therefore, in the above reference example , a swirl is generated in the intake air (air) sucked into the cylinder in the intake stroke in which the piston 1 moves downward in the cylinder, and then the piston 1 rises in the compression stroke of the cylinder. Then,
The swirl is the combustion chamber 4 in the recess 3 on the top surface of the piston 1.
Is pushed into the water and its flow velocity increases. A small-diameter circular arc portion 9 is formed on a wall surface of the annular space 5 which is an outer peripheral edge portion of the recessed portion 3 and corresponds to the rear end side. The small-diameter circular arc portion 9 has a cross-sectional center Os of the annular space 5. Is located on the outer side in the radial direction with respect to the position of the reference arc surface P having a radius R passing through on the wall surface and the radius R, and the arc radius r is smaller than the radius R of the reference arc surface P. As the number 9 projects outward from the position of the reference arc surface P, the moment of inertia becomes large, and the sustainability of the intake swirl in the combustion chamber 4 is further enhanced, and it strongly continues until the end of the combustion stroke.
【００２２】この後、ピストン１の上死点近傍で燃料噴
射ノズルから燃料が燃焼室４に向けて噴射され、その一
部の燃料流Ｆが突起部６先端のテーパ面７と凹陥部３の
開口部２との間を通って環状空間５の燃料流衝突部８に
衝突し、この衝突後の燃料は燃料流衝突部８から凹陥部
３の奥部に向かうが、その燃料流衝突部８の凹陥部３奥
部側には上記小径円弧部９があるので、そこでのエッジ
効果を受けて乱れが生じる。しかも、上記したように、
この小径円弧部９内で強い吸気スワールが持続している
ので、これら小径円弧部９での燃料流Ｆの乱れ及び吸気
スワールの相乗効果により、燃料の吸気とのミキシング
性が大幅に増大することとなり、よって燃料の燃焼性を
高めて排気ガス中のパティキュレートを効果的に低減す
ることができる。Thereafter, the fuel is injected from the fuel injection nozzle toward the combustion chamber 4 in the vicinity of the top dead center of the piston 1, and a part of the fuel flow F of the fuel flows from the tapered surface 7 at the tip of the protrusion 6 and the recessed portion 3. While colliding with the fuel flow collision portion 8 of the annular space 5 through the gap between the opening 2 and the fuel after the collision, the fuel flows from the fuel flow collision portion 8 to the inner portion of the recessed portion 3, but the fuel flow collision portion 8 Since there is the small-diameter circular arc portion 9 on the inner side of the concave portion 3, the edge effect there causes disturbance to occur. Moreover, as mentioned above,
Since a strong intake swirl continues in the small-diameter circular arc portion 9, the fuel flow F turbulence in the small-diameter circular arc portion 9 and the synergistic effect of the intake swirl significantly increase the mixing property of the fuel with the intake air. Therefore, the combustibility of the fuel can be improved and the particulate matter in the exhaust gas can be effectively reduced.
【００２３】そのとき、環状空間５の壁面における小径
円弧部９と突起部テーパ面７の外周部との間に、環状空
間５の断面中心Ｏs を中心とする基準円弧面Ｐの位置よ
りも半径方向内側に位置しかつ凹陥部３の奥部側に向か
って外径が拡大するテーパ面部１０が形成されているの
で、このテーパ面部１０により、燃焼室４の一部に断面
略円形状の環状空間５を持つ従来のディーゼルエンジン
に対し燃焼室４の容積が同じとなり、よって圧縮比を変
えることなく上記効果が得られる。At that time, between the small-diameter circular arc portion 9 on the wall surface of the annular space 5 and the outer peripheral portion of the projection tapered surface 7, the radius is larger than the position of the reference circular arc surface P centered on the cross-sectional center Os of the annular space 5. Since the tapered surface portion 10 that is located on the inner side in the direction and whose outer diameter increases toward the inner side of the recessed portion 3 is formed, the tapered surface portion 10 forms an annular shape having a substantially circular cross section in a part of the combustion chamber 4. The volume of the combustion chamber 4 becomes the same as that of the conventional diesel engine having the space 5, so that the above effect can be obtained without changing the compression ratio.
【００２４】（実施例）
図２は本発明の実施例を示し（尚、図１と同じ部分につ
いては同じ符号を付してその詳細な説明は省略する）、
この実施例では、上記突起部テーパ面７の中間部を凹陥
して、突起部テーパ面７を断面略円弧状としたものであ
る。( Embodiment ) FIG. 2 shows an embodiment of the present invention (note that the same parts as those in FIG. 1 are designated by the same reference numerals and detailed description thereof will be omitted).
In this embodiment, the intermediate portion of the projection tapered surface 7 is recessed so that the projection tapered surface 7 has a substantially arcuate cross section.
【００２５】この実施例では、ピストン１の上昇行程で
燃焼室４内に入る吸気が環状空間５に流れて突起部６先
端のテーパ面７と凹陥部３の開口部２との間で絞られる
際、上記突起部テーパ面７が断面略円弧状に凹陥されて
いるので、環状空間５に向かう吸気の一部が突起部テー
パ面７から開口部２側に向かうように案内される。そし
て、その後に燃料噴射ノズルから噴射された燃料流Ｆが
周辺の吸気を巻き込みながら環状空間５の燃料流衝突部
８に向かって飛ぶときに、この燃料流Ｆに上記突起部テ
ーパ面７で案内された吸気が向かうようになり、この吸
気により燃料への吸気の巻込み度が増大し、燃料への吸
気導入率が高まってミキシング効果がさらに増大し、パ
ティキュレートをより一層有効に低減することができ
る。 In this embodiment, intake air that enters the combustion chamber 4 in the upward stroke of the piston 1 flows into the annular space 5 and is narrowed between the tapered surface 7 at the tip of the projection 6 and the opening 2 of the recess 3. At this time, since the projection tapered surface 7 is recessed in a substantially arcuate cross section, a part of the intake air flowing toward the annular space 5 is guided from the projection tapered surface 7 toward the opening 2 side. Then, when the fuel flow F injected from the fuel injection nozzle flies toward the fuel flow collision portion 8 of the annular space 5 while entraining the surrounding intake air, the fuel flow F is guided to the fuel flow F by the protrusion tapered surface 7. The intake air is directed toward the intake air, which increases the degree of intake of the intake air into the fuel, increases the intake air intake rate into the fuel, further increases the mixing effect, and further effectively reduces the particulates. can.
【００２６】[0026]
【発明の効果】以上説明したように、請求項１の発明に
よると、ピストン頂面の燃焼室を形成する凹陥部底面に
先端にテーパ面を有する突起部を設け、その突起部の周
囲に断面略円形状の環状空間を形成してなる直噴式ディ
ーゼルエンジンの燃焼室構造において、環状空間の壁面
のうち凹陥部の外周縁部でかつ上記開口部近傍の位置
に、該環状空間の断面中心を中心とする円弧面からなっ
ていて燃料噴射ノズルから噴射される燃料流が衝突する
燃料流衝突部を設け、この燃料流衝突部の奥端部側の位
置に、燃料流衝突部の円弧面の半径よりも小径でかつ燃
料流衝突部の円弧面よりも半径方向外側に位置する小径
円弧部を設け、さらに突起部テーパ面を断面略円弧状に
凹陥させたことにより、この小径円弧部が他の壁面位置
から外側に突出している分だけ慣性モーメントが大とな
り、燃焼室での吸気スワールの持続性をさらに高めるこ
とができるとともに、ピストンの上死点近傍で燃料噴射
ノズルから燃焼室に向けて噴射された燃料流が環状空間
の壁面に衝突したとき、衝突後の燃料を小径円弧部での
エッジ効果により乱すことができる。さらに、突起部テ
ーパ面の断面略円弧状の凹陥構造により、ピストンの上
昇行程で燃焼室の環状空間に流れる吸気の一部を燃料噴
射ノズルからの燃料流に向かうように案内して、その燃
料流への吸気の巻込み度を増大させることができ、燃料
の吸気とのミキシング性を大幅に増大させてパティキュ
レートの効果的な低減を図ることができる。As described above, according to the invention of claim 1,
According to the above, the bottom of the recess that forms the combustion chamber on the top of the piston is
Provide a protrusion with a tapered surface at the tip, and
A direct injection type disc with an annular space with a substantially circular cross section
-The wall surface of the annular space in the combustion chamber structure of a diesel engine
Of the outer peripheral edge of the recess andPosition near the opening
The center of the cross section of the annular spaceConsists of an arc surface
And the fuel flow injected from the fuel injection nozzle collides
A fuel flow collision section is provided, and the position of the fuel flow collision section at the rear end side
The diameter of the arc surface of the fuel flow collision area is smaller than
Located radially outside the arc surface of the flow collision partSmall diameter
Arc section provided, Furthermore, the tapered surface of the protrusion has a substantially arcuate cross section.
DentAs a result, this small diameter circular arc is
The moment of inertia is large because it projects outward from
To further improve the sustainability of the intake swirl in the combustion chamber.
And the fuel injection near the top dead center of the piston
The fuel flow injected from the nozzle toward the combustion chamber is an annular space
When colliding with the wall surface of the
Can be disturbed by the edge effectIt In addition, the protrusion
The upper surface of the piston is
During the ascending stroke, part of the intake air flowing into the annular space of the combustion chamber is injected with fuel.
Guide the fuel flow from the injection nozzle to the fuel
It is possible to increase the degree of entrainment of intake air into the flow,fuel
It greatly increases the mixing property with the intake of
The rate can be effectively reduced.
【００２７】請求項２の発明によると、上記環状空間の
壁面における小径円弧部の半径方向内側に、凹陥部の奥
部側に向かって外径が拡大するテーパ面部を形成したこ
とにより、燃焼室の一部に断面略円形状の環状空間を持
つ従来のディーゼルエンジンに対し燃焼室の容積つまり
圧縮比を変えることなく、上記効果が得られる。[0027] According to the second aspect of the present invention, this in a radial direction inner side of the small-diameter arcuate portion of the wall surface of the annular space to form a tapered surface portion having an outer diameter expands toward the innermost side of the recessed Recessed portion
With the above, the above effect can be obtained without changing the volume of the combustion chamber, that is, the compression ratio, as compared with the conventional diesel engine having an annular space having a substantially circular cross section in a part of the combustion chamber.
【図１】参考例に係る燃焼室構造を示す断面図である。FIG. 1 is a cross-sectional view showing a combustion chamber structure according to a reference example .
【図２】本発明の実施例を示す図１相当図である。FIG. 2 is a view corresponding to FIG. 1 showing an embodiment of the present invention .
【図３】従来例を示す図１相当図である。FIG. 3 is a view corresponding to FIG. 1 showing a conventional example.
１ ピストン
２ 開口部
３ 凹陥部
４ 燃焼室
５ 環状空間
６，６′ 突起部
７ 突起部テーパ面８
燃料流衝突部
９ 小径円弧部
１０ テーパ面部
１１ 平面部
Ｏs 環状空間の断面中心
Ｐ 環状空間の断面中心を中心としかつ壁面上を通る基
準円弧面
Ｒ 基準円弧面の半径
Ｒc 凹陥部の開口半径
ｒ 小径円弧部の半径
Ｆ 燃料流1 Piston 2 Opening 3 Recess 4 Combustion Chamber 5 Annular Space 6, 6'Projection 7 Projection Tapered Surface 8 Fuel Flow Collision 9 Small Diameter Arc 10 Tapered Surface 11 Flat Surface Os Cross Section Center P of Annular Space Reference arc surface R centering on the center of the cross section and passing on the wall surface Radius Rc of the reference arc surface R Radius of the recessed portion r Radius of the small diameter arc portion F Fuel flow
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平４−295130（ＪＰ，Ａ) 特開 平３−249326（ＪＰ，Ａ) 特開 平４−339130（ＪＰ，Ａ) 実開 平３−32124（ＪＰ，Ｕ) 実開 平２−20720（ＪＰ，Ｕ) (58)調査した分野(Int.Cl.7，ＤＢ名) F02B 23/06 F02F 3/26 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-295130 (JP, A) JP-A-3-249326 (JP, A) JP-A-4-339130 (JP, A) Actual Kaihei 3- 32124 (JP, U) Actual Kaihei 2-20720 (JP, U) (58) Fields investigated (Int.Cl. 7 , DB name) F02B 23/06 F02F 3/26
Claims (2)
部よりも大きくて燃焼室を形成する凹陥部が設けられ、
上記凹陥部の底面中央に凹陥部の開口側に突出する突起
部が形成されていて、この突起部の先端外周部に凹陥部
の奥部側に向かって外径が拡大する突起部テーパ面が凹
陥部の開口部と対峙するように形成され、上記突起部の
外周部と凹陥部の開口部との間に断面略円形状の環状空
間が突起部を取り囲むように設けられた直噴式ディーゼ
ルエンジンの燃焼室構造において、 上記環状空間の壁面のうち凹陥部の外周縁部でかつ上記
開口部近傍の位置には、該環状空間の断面中心を中心と
する所定半径の円弧面からなっていて燃料噴射ノズルか
ら噴射される燃料流が衝突する燃料流衝突部が設けられ
ている一方、 上記環状空間の壁面のうち上記燃料流衝突部の奥端部側
の位置には、燃料流衝突部の円弧面の半径よりも小径で
かつ該燃料流衝突部の円弧面よりも半径方向外側に位置
する 小径円弧部が他の壁面と連続するように設けられ、 上記突起部テーパ面が断面略円弧状に凹陥され ているこ
とを特徴とする直噴式ディーゼルエンジンの燃焼室構
造。1. A top surface of a piston is provided with a recessed portion having an inner diameter on the inner side larger than that of an opening and forming a combustion chamber,
A protrusion protruding toward the opening side of the recess is formed in the center of the bottom surface of the recess, and a protrusion tapered surface whose outer diameter increases toward the inner side of the recess is formed on the outer periphery of the tip of the protrusion. An annular space, which is formed to face the opening of the recess and has a substantially circular cross section, is provided between the outer periphery of the protrusion and the opening of the recess so as to surround the protrusion. in the combustion chamber structure for a direct injection diesel engine, and the outer peripheral edge portion of the recessed portion of the wall surface of the annular space
At the position near the opening, the cross-sectional center of the annular space is centered
A fuel injection nozzle that has an arc surface with a predetermined radius
Is provided with a fuel flow impingement portion against which the fuel flow injected from
On the other hand, on the wall surface of the annular space, the rear end side of the fuel flow collision portion
Is smaller than the radius of the arc surface of the fuel flow collision part.
And located radially outside the arc surface of the fuel flow collision portion
A combustion chamber structure of the small-diameter arcuate portion is provided so as to continue communication with the other wall, direct injection diesel engine, characterized in that the protrusions taper surface is recessed in a substantially arc shape.
ンの燃焼室構造において、 環状空間の壁面における小径円弧部の半径方向内側に
は、凹陥部の奥部側に向かって外径が拡大するテーパ面
部が小径円弧部に連続するように形成されていることを
特徴とする直噴式ディーゼルエンジンの燃焼室構造。 2. The direct-injection diesel engine combustion chamber structure according to claim 1, wherein the small-diameter circular arc portion is radially inside the wall surface of the annular space.
The combustion chamber structure of a direct injection diesel engine, wherein a tapered surface portion to increase the outer diameter toward the innermost side of the recessed portion is formed so as to continue with the small-diameter arcuate portion.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01245693A JP3370123B2 (en) | 1993-01-28 | 1993-01-28 | Combustion chamber structure of direct injection diesel engine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP01245693A JP3370123B2 (en) | 1993-01-28 | 1993-01-28 | Combustion chamber structure of direct injection diesel engine |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06221162A JPH06221162A (en) | 1994-08-09 |
| JP3370123B2 true JP3370123B2 (en) | 2003-01-27 |
Family
ID=11805851
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP01245693A Expired - Fee Related JP3370123B2 (en) | 1993-01-28 | 1993-01-28 | Combustion chamber structure of direct injection diesel engine |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3370123B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006112312A (en) * | 2004-10-14 | 2006-04-27 | Yanmar Co Ltd | Combustion chamber shape for direct injection type diesel engine |
| DE102005060547A1 (en) | 2005-12-17 | 2007-06-28 | Mahle International Gmbh | Automotive piston for fuel-injected engine has profiled central combustion cavity with rounded edges |
| JP5227010B2 (en) * | 2007-12-21 | 2013-07-03 | 三菱自動車工業株式会社 | Piston for direct injection diesel engine |
| DE102009050265A1 (en) * | 2009-10-21 | 2010-09-02 | Mtu Friedrichshafen Gmbh | Piston for internal-combustion engine, particularly for air-consolidating internal-combustion engine, has upper surface contour of piston base |
-
1993
- 1993-01-28 JP JP01245693A patent/JP3370123B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06221162A (en) | 1994-08-09 |
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